Seasonal movements of sediment in the Tamar estuary have been estimated by recording variations in sediment levels at 30 sites evenly distributed along the length of the estuary through a fourteen month period. The Tamar estuary, situated in the south west of England, extends 31km from a weir at Gunnislake to its mouth at Plymouth Sound. Thirty wooden poles, each 2m long and 4cm square, were treated with a wood preservative and driven vertically into the intertidal mud at roughly 1km intervals along the estuary. The poles were positioned such that they were uncovered at tidal elevations between low water neaps and low water springs. After allowing one month for site recovery from disturbance during installation, measurements of sediment level relative to each pole were taken monthly during spring tides at low water. The study was started in December 1981 and continued for 14 months.